curl -X GET "https://example.com/v1/unsubscribe?token=string""string"Rotate Secret
Generate a new signing secret and immediately invalidate the old one. The response includes the new plaintext secret — this is the only time it is returned; update your verification code with it right away, since the old secret stops validating new deliveries immediately.
Create Email Attachment
Upload a file and get back a reusable attachment id. The returned id can be referenced from attachment_ids on many later POST /v1/emails calls until it is garbage-collected for being unused; it is not deleted immediately after first use. Uploads are size-limited and scoped to the caller's organization.